Alfalfa winter cutting: Effectiveness against the alfalfa weevil, Hypera postica (Gyllenhal) (Coleoptera: Curculionidae) and effect on its rate of parasitism due to Bathyplectes spp. (Hymenoptera: Ichneumonidae)

Abstract

The alfalfa weevil Hypera postica (Gyllenhal) (Coleoptera: Curculionidae) is a major pest of alfalfa worldwide. In Spain, insecticide sprayings are mainly used for control with low efficacy. As a potential more sustainable control method, we determined the effectiveness of an alfalfa winter cutting for reducing pest populations in the spring and its interaction with parasitism rate due to Bathyplectes spp. (Hymenoptera: Ichneumonidae). Forty-two commercial fields were split in two parts and one was mowed during winter. Larval abundance in each part of the field was sampled by sweep netting in 2019 and 2020 before the first alfalfa spring cutting, when damage is caused. The rates of parasitism due to Bathyplectes anura (Thomson) and Bathyplectes curculionis (Thomson) were estimated by rearing larvae in the laboratory. Winter cutting significantly reduced the spring larval weevil populations and favored the rate of larval parasitism. Our results suggest that winter cutting can be a useful cultural method for alfalfa weevil control that has potential to be a component of an integrated pest management program.